Solid state light with optical guide and integrated thermal guide

ABSTRACT

A solid state light having a solid state light source such as LEDs, and optical guide, and a thermal guide. The optical guide is coupled to the light source for receiving and distributing light from the light source, and the thermal guide is integrated with the optical guide for providing thermal conduction from the solid state light source and dissipating heat through convection for cooling the light.

BACKGROUND

The energy efficiency of lighting has become an important considerationin industrial, consumer, and architectural lighting applications. Withthe advances in solid state light technology, light emitting diodes(LEDs) have become more energy efficient than fluorescent lights.Further, the marketplace has a large established fixture base forEdison, fluorescent and high intensity discharge lights. These types ofapplications present a significant technical challenge for LEDs due totheir inherent point source nature, and the need to operate the LEDs atrelatively low temperatures. Today there are many solutions addressingthese issues, including fans, thermal sinks, heat pipes and the like.However, these approaches limit the applications by adding complexity,cost, efficiency loss, added failure modes, and an undesirable formfactor. The need remains to find a solution that can provide optical andefficiency benefits, at attractive manufacturing costs and design.

SUMMARY

A light, consistent with the present invention, includes a light source,an optical guide, and a thermal guide. The optical guide is coupled tothe light source for receiving and distributing light from the lightsource, and the thermal guide is integrated with the optical guide forproviding thermal conduction from the light source for cooling thelight.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and constitute a part ofthis specification and, together with the description, explain theadvantages and principles of the invention. In the drawings,

FIG. 1 is a diagram illustrating a solid state light source with anoptical guide and integrated thermal guide;

FIG. 2 is a perspective view of a solid state light using an opticalguide sheet and co-extensive thermal guide;

FIG. 3 is a side view of the light of FIG. 2;

FIG. 4 is a perspective view of a solid state light using an opticalguide sheet and dual co-extensive thermal guides;

FIG. 5 is a side view of the light of FIG. 4;

FIG. 6 is a cross sectional side view of a solid state light using anoptical guide having an exterior portion for emitting light and aninterior portion for cooling;

FIG. 7 is a top view of the light of FIG. 6;

FIG. 8 is a bottom view of the light of FIG. 6;

FIG. 9 is a cross sectional side view of a solid state light with anactive cooling element;

FIG. 10 is a side view of a solid state light with a thermal guidehaving an air passage;

FIG. 11 is a top view of the light of FIG. 10;

FIG. 12 is a side view of a solid state light with a thermal guidehaving an air passage;

FIG. 13 is a top view of the light of FIG. 12;

FIG. 14 is a side view of a solid state light with a thermal guidehaving a single aperture;

FIG. 15 is a top view of the light of FIG. 14;

FIG. 16 is a diagram illustrating an optical guide with light extractionfeatures;

FIG. 17 is a diagram illustrating an optical guide with apertures forcooling or as extraction features;

FIG. 18 is a diagram illustrating an optical guide with a reflectivelayer;

FIG. 19 is a top view of a heat spreader prior to forming features thatcouple to fins for the thermal guide;

FIG. 20 is a top view of the heat spreader of FIG. 19 after forming thefeatures;

FIG. 21 is a side view of the heat spreader of FIG. 19 after forming thefeatures; and

FIG. 22 is a top view of the heat spreader of FIG. 19 after forming thefeatures.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating components of a light 10 having a powercircuit 12, a solid state light source 14, and a thermo optical guidecomprising an optical guide 16 and an integrated thermal guide 18. Powercircuit 12 receives power from a power supply and provides the requiredvoltage and current to drive solid state light source 14, which isoptically coupled to optical guide 16. In particular, solid state lightsource 14 injects light into optical guide 16, which receives anddistributes the light. Optical guide 16 includes light injection, lighttransport, and light extraction zones or elements in order to distributethe light.

Thermal guide 18 is integrated with optical guide 16 in order to drawheat from solid state light source 14 through conduction and dissipatethe heat through convection to cool light 10 and to efficiently utilizeboth area and volume for the cooling. Thermal guide 18 includes heatacquisition, heat spreading, and heat dissipation zones or elements inorder to cool the light. Through integration of the optical and thermalguides, embodiments of this invention overcome many of the limitationsof current solid state light concepts such as those identified above.

Solid state light source 14 can be implemented with, for example, LEDs,organic light emitting diodes (OLEDs), or other solid state lightsources. Certain embodiments can provide for uniformly distributed lightfrom the solid state light source. Alternatively, lenses can be used tofocus the emitted light. For example, in certain embodiments the lightcan produce a cone or curtain of light. The lenses could have airpermeability for cooling and can include Fresnel lenses, prismaticstructures, or lenslet structures. The solid state light sources canemit light of various colors for decorative or other lighting effects.Solid state light source 14 is electrically connected with power circuit12, which can include a flexible circuit or other circuitry for poweringthe solid state light source. The circuitry to power the light sourcecan include dimming circuitry and electronics to control frequencyshifting or color shifting components that help produce a more desirablelight, and an example of such electronics are described in U.S. patentapplication Ser. No. 12/137667, entitled “AC Illumination Apparatus withAmplitude Partitioning,” and filed Jun. 12, 2008, which is incorporatedherein by reference as if fully set forth.

Optical guide 16 can be implemented with, for example, a transparent ortranslucent material capable of receiving light from the solid statelight source and emitting the light. For example, optical guide 16preferably is made of an optically suitable material such aspolycarbonate, polyacrylates such as polymethyl methacrylate,polystyrene, glass, or any number of different plastic materials havingrelatively high refractive indexes. The optical guide can be configuredin a variety of shapes such as a bulb, sphere, cylinder, cube, sheet, orother shape. Furthermore, the optical guide can include a matrixmaterial that can contain light frequency shifting chromaphores toobtain a more desirable color rendering index, and examples of matrixstabilized dyes are described in U.S. Pat. No. 5,387,458, which isincorporated herein by reference as if fully set forth.

Thermal guide 18 can be implemented with a material capable ofconducting heat from the solid state light source and dissipating theheat. For example, the thermal guide is preferably comprised of amaterial with a thermal conductivity from about 1 W/(m-K) to 1000W/(m-K), and more preferably from 10 W/(m-K) to 1000 W/(m-K), and mostpreferable from 100 W/(m-K) to 1000 W/(m-K). The thermal guide drawsheat from the solid state light source through conduction and dissipatesheat into air through convection. Optionally, components of the thermalguide can include heat pipes. The thermal guide is integrated with theoptical guide, meaning that the thermal guide is in sufficient contact,directly or indirectly, with the solid state light source in order toconduct and dissipate heat from the solid state light source for thelight to function. For example, the thermal guide can draw heat from thesolid state light sources to maintain the light sources cool enough tofunction as intended. The thermal guide can be directly in physicalcontact with the solid state light sources or indirectly in contact withthem such as through a ring or other components upon which the solidstate light sources are mounted. The thermal guide can also be inphysical contact with the optical guide, either directly or indirectlythrough other components. Alternatively, the thermal guide need not bein physical contact with the optical guide, provided that the thermalguide can conduct sufficient heat from the solid state light sources inorder for the light to function. Therefore, the thermal guide resideseither co-extensively proximate at least a portion or preferably amajority of the area of the optical guide, or the thermal guide resideswithin at least a portion or preferably a majority of the volume of theoptical guide in the case of a bulb, sphere or other three dimensionalshape having an interior volume.

The thermal guide can include thermal conductive enhancements such asmetal coatings or layers, or conductive particles, to help conduct theheat generated by the solid state light sources into and along thethermal guide. Further, the thermal guide can have convective thermalenhancements such as fins and microstructures to increase the convectiveheat transfer coefficient. The thermal guide can also have opticalenhancements in order to enhance the light output of the optical guide.For example, the thermal guide can be formed from a reflective materialor a material modified to have a reflective surface such as white paint,a polished surface, or a thin reflective material on its surface.

FIGS. 2 and 3 are perspective and side views, respectively, of a solidstate light 20 using an optical guide sheet 24 and co-extensive thermalguide 22. Light 20 includes a plurality of solid state light sources 26optically coupled with optical guide sheet 24. For example, solid statelight sources 26 can be located within hemispherical or other types ofdepressions in the edge of optical guide sheet 24 and possibly securedthrough use of an optically clear adhesive. Optical guide sheet 24distributes light from the solid state light sources 26 through anemission surface 28, and it can be configured to provide substantiallyuniform distribution of light across surface 28. Thermal guide 22 isintegrated with optical guide 24 by being sufficiently co-extensive andin physical proximity with it in order to draw heat away from solidstate light sources 26 and dissipate the heat to maintain light 28 coolenough to function.

FIGS. 4 and 5 are perspective and side views, respectively, of a solidstate light 30 using an optical guide sheet 34 and dual co-extensivethermal guides 32 and 36. Light 30 includes a plurality of solid statelight sources 38 optically coupled with optical guide sheet 34. Forexample, solid state light sources 38 can be located withinhemispherical or other types of depressions in the edge of optical guidesheet 34 and possibly secured through use of an optically clearadhesive. Optical guide sheet 34 distributes light from the solid statelight sources through an emission end 40, and it can be configured toprovide substantially uniform distribution of light from end 40. Thermalguides 32 and 36 are integrated with optical guide 34 by beingsufficiently co-extensive and in physical proximity with it in order todraw heat away from solid state light sources 38 and dissipate the heatto maintain light 30 cool enough to function.

For lights 20 and 30, the optical guide and co-extensive thermal guidecan be configured in a variety of shapes, aside from planar. Forexample, they can be formed in a circle, spiral, or a non-planar shapefor decorative or other lighting effects. The optical guide can beformed from, for example, polycarbonate, polyacrylates such aspolymethyl methacrylate, polystyrene, glass, or any number of differentplastic materials having relatively high refractive indexes. Theco-extensive thermal guides can be formed, for example, as a metalliccoating on the optical guide.

FIG. 6 is a cross sectional side view of a preferred embodiment of asolid state light 42 using an optical guide having an exterior portionfor emitting light and an interior portion for cooling. FIGS. 7 and 8are top and bottom views, respectively of light 42. Light 42 includes anoptical guide 52, integrated thermal guide 54, and solid state lightsources on an optional heat spreader ring 46. The heat spreader ring 46can operate by thermal conduction or have a heat pipe or thermal siphonassociated with it. The heat spreader ring contains elements thatefficiently connect to the thermal guide, an example of which includes aring containing bent fin elements that are thermally connected to thethermal guide. Alternatively, the solid state light sources can becoupled directly to a thermal guide without a heat spreader ring. Forthe solid state light sources, light 42 can include, for example, LEDs48, 50, 66, 68, 70, and 72 arranged around ring 46, as shown in FIG. 8.The solid state light sources are optically coupled to optical guide 52;for example, the light sources can be located within hemispherical orother types of depressions in an edge of optical guide 52 and possiblysecured through use of an optically clear adhesive.

A base 44 is configured to connect to a power supply, and it can includea power circuit for providing the required voltage and current from thepower supply to drive the solid state light sources. Base 44 can beimplemented with, for example, an Edison base for use with conventionallight bulb sockets or a base for use with conventional fluorescent lightfixture connections. Air passages 56 and 58 are provided between opticalguide 52 and base 44 to provide free convection across thermal guide 54through an air passage 60.

In this exemplary embodiment, the thermal guide is implemented withmetallic fins 54, 62, and 64, as illustrated in FIG. 7. The fins areintegrated with light guide 52, as shown in FIGS. 7 and 8, in order todraw heat from solid state light sources 48, 50, 66, 68, 70, 72 anddissipate the heat through convection by air flow in air passage 60. Thethermal guide can optionally include a heat pipe or thermal siphon.Optical guide 52 can be implemented with, for example, polycarbonate,polyacrylates such as polymethyl methacrylate, polystyrene, glass, orany number of different plastic materials having relatively highrefractive indexes.

The exterior portion of light 42 can be used to distribute and emitlight from the solid state light sources, and the interior portion oflight 42 is used for cooling the thermal guide and solid state lightsources. Optical guide 52 can be formed in a bulb shape, as representedin FIG. 6, or in other shapes. With certain shapes, such as a bulb shapeshown in FIG. 6, the interior portion of optical guide 52 can form aninterior volume, and the thermal guide can be integrated with theinterior volume of the optical guide for providing thermal conductionfrom the solid state light sources.

FIG. 9 is a cross sectional side view of a solid state light 74 with anactive cooling element 88. Light 74 can have a similar construction aslight 42. Light 74 includes a base 76, an optical guide 84, a thermalguide 86, and solid state light sources, such as LEDs 80 and 82,arranged on an optional heat spreader ring 78. Active cooling element88, such as a fan, draws air through air passage 87 for cooling inaddition to free convection. Active cooling element 88 can be coupled toa power source through base 76, and it can run continuously when light74 is in operation or can include a temperature sensor to active it onlywhen light 74 is above a certain temperature.

FIGS. 10-15 illustrate additional configurations of solid state lightshaving an optical guide with an exterior portion for emitting light andan interior portion for cooling via an integrated thermal guide. Theycan function in a manner similar to light 42 as described above. FIGS.10 and 11 are side and top views, respectively, of a solid state light90 with a perforated air passage opening. Light 90 includes a base 92for connection to a power supply, an optical guide 98 for distributinglight, an air passage 100 through optical guide 98, and a thermal guideassociated with optical guide 98. The thermal guide includes fins 102, aring 94, and a perforated portion 96 between base 92 and ring 94.Perforated portion 96 allows for air flow through air passage 100. Fins102 of the thermal guide conduct heat from ring 94 and dissipate theheat through convection in air passage 100.

FIGS. 12 and 13 are side and top views, respectively, of a solid statelight 104 with a thermal guide having plurality of apertures. Light 104includes a base 106 for connection to a power supply, an optical guide114 for distributing light, an air passage 116 through optical guide114, and a thermal guide associated with optical guide 114. The thermalguide includes fins 118, a ring 108, and a section 110 having aplurality of apertures 112 between base 106 and ring 108. Apertures 112allow for air flow through air passage 116. Fins 118 of the thermalguide conduct heat from ring 108 and dissipate the heat throughconvection in air passage 116.

FIGS. 14 and 15 are side and top views, respectively, of a solid statelight 120 with a thermal guide having a single aperture. Light 120includes a base 122 for connection to a power supply, an optical guide130 for distributing light, an air passage 132 through optical guide130, and a thermal guide associated with optical guide 130. The thermalguide includes fins 134, a ring 124, and a section 126 having anaperture 128 between base 122 and ring 124. Aperture 128 allows for airflow through air passage 132. Fins 134 of the thermal guide conduct heatfrom ring 124 and dissipate the heat through convection in air passage132.

FIGS. 16-18 illustrate various optional features for an optical guidefor the solid state lights described above. FIG. 16 is a diagramillustrating an optical guide 140 with light extraction features 142.Such light extraction features can be used to provide for greater ormore uniform distribution of light emitted by the optical guide, or theextraction features can provide for particular optical effects such astailoring the light pattern for particular illumination patterns.Examples of extraction features include a pattern of dots or othershapes of light extraction material printed or otherwise affixed ontothe exterior or interior surface of the optical guide. Extractionfeatures can also include roughening of the exterior of the opticalguide through sandblasting or other techniques, and other extractionfeatures include microstructured features formed on a surface such asmicrostructured prisms or lenslets.

FIG. 17 is a diagram illustrating an optical guide 144 with apertures146 for cooling. If the solid state light is mounted substantiallyhorizontally, apertures 146 can provide for air flow through the opticalguide and across the thermal guide for the cooling though convectionrather than air flow substantially along the interior surface of theoptical guide such as through air passage 60. Apertures 146 can alsofunction as extraction features.

FIG. 18 is a diagram illustrating an optical guide 148 with a reflectivelayer 150. Optical guide 148 can include reflective layer 150 on itsinterior surface such that a portion of light distributed throughoptical guide 148 is reflected by reflective layer 150 and emitted fromexterior surface 152 rather than being emitted from the interior surfaceof the optical guide. An example of a reflective layer is the EnhancedSpecular Reflective (ESR) film product available from 3M Company.

FIGS. 19-22 illustrate a heat spreader 160 with features for use inmounting fins of a thermal guide. FIG. 19 is a top view of heat spreader160 prior to forming the features that couple to fins for the thermalguide. FIGS. 20, 21, and 22 are top, side, and perspective view,respectively, of heat spreader 160 after forming the features. Heatspreader 160 can operate in a manner similar to heat spreader ring 46 asdescribed above but with the additional features for mounting coolingfins for connection with the thermal guide.

As shown in FIG. 19, heat spreader 160 has a ring portion 162 andtriangularly shaped sections 164, 166, 168, and 170. In a manufacturingprocess, heat spreader 160 can be formed from a sheet of metal or othermaterial. For example, a stamping process can be used to cut heatspreader 160 from the sheet of metal and bend sections 164, 166, 168,and 170 to substantially right angles to ring portion 162, as shown inFIGS. 20-22, forming upward protrusions.

The solid state light sources can be mounted on ring portion 162 in amanner similar to the LEDs mounted on heat spreader ring 46. Coolingfins of a thermal guide, such as the fins described above, can bethermally connected to sections 164, 166, 168, and 170 such as throughsoldering, conductive epoxy, clips, or in other ways. In that manner,heat spreader 160 with the mounting features effectively becomes part ofthe thermal guide and can be easily manufactured from a sheet ofmaterial. Four triangularly shaped sections 164, 166, 168, and 170 areshown for illustrative purposes only. More or fewer features can beused, and the features can have various shapes, depending upon, forexample, a configuration of the cooling fins to which they are to beconnected.

1. A light with integrated light and thermal guides, comprising: a lightsource; a light guide coupled to the light source for receiving anddistributing light from the light source, wherein the light istransported within the light guide until the light exits from a surfaceof the light guide; and a thermal guide integrated with the light guidefor providing thermal conduction from the light source for cooling thelight, wherein the thermal guide comprises a solid material capable ofconducting heat from the light source and dissipating the heat, whereinthe light guide comprises a material having a first surface and a secondsurface opposite the first surface and an edge between the first andsecond surfaces, the light exits from the first or second surface, andthe light with the integrated light and thermal guides provides for airflow proximate the first and second surfaces, wherein the light sourceis located at the edge of the light guide in order to optically couplethe light into the light guide at the edge, wherein the light includes alight frequency shifting material.
 2. The light of claim 1, wherein thelight frequency shifting material comprises a dye.
 3. A light withintegrated light and thermal guides, comprising: a light source; a lightguide coupled to the light source for receiving and distributing lightfrom the light source, wherein the light is transported within the lightguide until the light exits from a surface of the light guide; and athermal guide integrated with the light guide for providing thermalconduction from the light source for cooling the light, wherein thethermal guide comprises a solid material capable of conducting heat fromthe light source and dissipating the heat, wherein the light guidecomprises a material having a first surface and a second surfaceopposite the first surface and an edge between the first and secondsurfaces, the light exits from the first or second surface, and thelight with the integrated light and thermal guides provides for air flowproximate the first and second surfaces, wherein the light source islocated at the edge of the light guide in order to optically couple thelight into the light guide at the edge, wherein the light guidecomprises a sheet of material having a non-planar shape.
 4. The light ofclaim 3, wherein the first or second surface of the light guide includeslight extraction features.
 5. The light of claim 4, wherein the lightextraction features comprise a pattern of dots.
 6. The light of claim 4,wherein the light extraction features comprise prisms.
 7. The light ofclaim 4, wherein the light extraction features comprise lenslets.
 8. Thelight of claim 3, further comprising a reflective layer on one side ofthe light guide.
 9. A light with integrated light and thermal guides,comprising: a light source; a light guide comprising a material having afirst surface and a second surface opposite the first surface and anedge between the first and second surfaces, wherein the second surfaceforms an interior volume, the light guide is coupled to the light sourcefor receiving and distributing light from the light source through thefirst or second surface, and the light is transported within the lightguide until the light exits from the first or second surface of thelight guide, wherein the light source is located at the edge of thelight guide in order to optically couple the light into the light guideat the edge; and a thermal guide at least partially contained within theinterior volume and integrated with the light guide for providingthermal conduction from the light source for cooling the light, whereinthe thermal guide comprises a solid material capable of conducting heatfrom the light source and dissipating the heat, wherein the lightincludes a light frequency shifting material.
 10. The light of claim 9,wherein the light frequency shifting material comprises a dye.
 11. Alight with integrated light and thermal guides, comprising: a lightsource; a light guide comprising a material having a first surface and asecond surface opposite the first surface and an edge between the firstand second surfaces, wherein the second surface forms an interiorvolume, the light guide is coupled to the light source for receiving anddistributing light from the light source through the first or secondsurface, and the light is transported within the light guide until thelight exits from the first or second surface of the light guide, whereinthe light source is located at the edge of the light guide in order tooptically couple the light into the light guide at the edge; and athermal guide at least partially contained within the interior volumeand integrated with the light guide for providing thermal conductionfrom the light source for cooling the light, wherein the thermal guidecomprises a solid material capable of conducting heat from the lightsource and dissipating the heat, wherein the light guide comprises aspherical shape.
 12. The light of claim 11, wherein the first or secondsurface of the light guide includes light extraction features.
 13. Thelight of claim 12, wherein the light extraction features comprise apattern of dots.
 14. The light of claim 12, wherein the light extractionfeatures comprise prisms.
 15. The light of claim 12, wherein the lightextraction features comprise lenslets.
 16. The light of claim 11,wherein the light guide includes a plurality of apertures.